We are studying mental health and mental illness in the aged by studies of behavior, some aspects of cerebral neurophysiology and imaging of brain structure in vivo. Our objectives are (1) the analysis of the value of various behavioral and biomedical factors in predicting the development of severe senile dementia, and (2) a study of the interrelationships of behavioral and biomedical data derived from serial testing of the aged. One hundred subjects aged 65 to 75, fifty thought to be in the early phase of senile dementia and fifty matched controls, will be studied serially over a two-year period with medical evaluation, clinical neuropsychiatric assessment, psychometric studies, advanced analysis of the visual evoked esponse (VER) and quantitative computerized cranial tomography (CT). Data analysis will reveal (1) the predictive value when performed serially in the same patient of the tests (alone and in combination) regarding the clinical course of senile dementia as opposed to normal aging, and (2) the interdependencies of the various clinical, behavioral, physiological and brain structural data. Subjects will be followed thereafter until autopsy when half of the brain will be prepared for neuropathological examination and half preserved for future morphologic, chemical and other studies.